Valerie Messick is the widow of Gambino mob accountant Phillip Messick. Valerie was nearly killed during Phillip's murder by hitman Jay Fleckner, in an attempt to stop the Jessica's from being witnesses once the FBI closed in on the operations.
Valerie perjured her testimony just to get Fleckner released, only to order friend and accomplice, dirty cop Bob Cerullo, to murder Fleckner. Valerie demanded immunity in exchange for testifying to convict Cerullo, which was granted. (L&O: "Family Friend")